The present invention relates to new crystals of nateglinide (the chemical name: N-(trans-4-isopropylcyclohexylcarbonyl)-D-phenylalanine) and methods for producing nateglinide B-type crystals from them. More specifically, the present invention relates to nateglinide A-type crystals, M-type crystals and P-type crystals, methods for producing them and methods for producing nateglinide B-type crystals from those crystals.
Nateglinide represented by general formula 1 given below is used as a therapeutic agent for diabetes in Japan and also in Western countries because it effectively lowers blood glucose. This compound is described in Japanese Patent Publication No. Hei 4-15221. According to this publication and Japanese Patent No. 2,508,949, it is known that this compound has B-type and H-type crystals. It was confirmed that B-type crystals are obtained by, for example, crystallizing them from methanol/water and then drying them under heating and that the melting point of the crystals is 129-130° C. On the other hand, nateglinide H-type crystals are described in Japanese Patent No. 2,508,949 and the melting point thereof is confirmed to be 136 to 142° C.
